Me to, but for me it's always for a bit more of a calorie burn and more tension even if it's not the best tension to grow its tension lol!

Forced reps are one of the best ways to increase hypertrophy in a muscle. Not that I recommend them over proper technique but it's one of the only ways to truly bring a muscle group to full exhaustion. Especially using forced reps with a focus on the eccentric portion of the lift.

I'd agree with the genetic crowd for the most part. I always had longer slender bis and until I just gained overall BW, (going from say #195 to #235) my bis finally got fuller. No extra arm work really and in fact probably less emphasis on bis, just tons of "heavy" back work, chins, rows, low cable pulls etc etc.